1. Field of the Invention
This invention relates to a stereoscopic image processing apparatus arranged to record on a recording medium a stereoscopic image signal corresponding to a stereoscopic image which is composed of, for example, left and right images or to reproduce from the recording medium and display the stereoscopic image thus recorded.
2. Description of the Related Art
FIG. 1 roughly shows the essential parts of the conventional TV system. Referring to FIG. 1, the system includes an antenna 46 which is provided for receiving image information sent from various broadcasting stations. A video tape recorder (VTR) 47 is arranged to receive the image information through the antenna 46 and to record the image information on a video tape.
Further, in reproducing and displaying the image information, the VTR 47 reads out from the video tape a desired part of the image information. The image information read out is sent to a TV monitor 48 to output images and sounds relative to them from the TV monitor 48.
The number of programs of image information has rapidly increased during recent years. The method for supplying these programs also has been diversified to include ground broadcasting, satellite broadcasting, cable broadcasting, etc. As a result, the number of programs concurrently available has increased.
The kinds of image information recording media also have increased to include optical disks, etc., besides video tapes. These recording media have come to permit recording images at a high degree of definition over a long period of time. For example, some of the VTRs of the NTSC system has, in addition to a standard mode, a triple mode in which image information can be recorded and reproduced over a length of time which is three times as long as the recordable length in the standard mode.
Meanwhile, a stereoscopic image display apparatus for viewing a stereoscopic image has been contrived with a parallax between two eyes utilized for giving a vividly lifelike image. A method for making a stereoscopic image viewable with this stereoscopic image display is as follows: An image is picked up, for example, by arranging two image pickup systems by separating their optical axes as much as a distance corresponding to a distance between the left and right eyes of the viewer (a parallax or a base length). The two images thus obtained from the two image pickup systems (hereinafter referred to as images with a parallax), i.e., the image for the right eye, and the image for the left eye are linearly polarized in different directions. These images are then compositely displayed by utilizing the differently polarized state. The viewer sees the images individually with right and left eyes by using polarizing filter spectacles.
According to another method, the stereoscopic image display apparatus is arranged to operate as follows: An image for the right eye and an image for the left eye are displayed in a time sharing manner. In viewing the display, time-division shutter spectacles are used in synchronism with the display of the images to see them individually with the right and left eyes.
FIG. 2 shows in outline the essential parts of a stereoscopic image display apparatus arranged to be used by the viewer by mounting it on a helmet or goggles. The illustration includes a liquid crystal display 49 for the left eye and a liquid crystal display 50 for the right eye. As mentioned above, images which are obtained in the above-stated manner respectively for the left and right eyes 33 and 34 of the viewer are displayed.
The liquid crystal displays 49 and 50 are illuminated from behind by a back light 22, and images displayed on them are individually viewed respectively by the left and right eyes 33 and 34 through reflection mirrors 51 and 52 and lenses 53 and 54.
The performance of the VTRs of the kind used as shown in FIG. 1 has advanced both in image quality and in the length of recordable time. As a result, they have come to use recording media of varied kinds. However, no VTR has been arranged to be capable of simultaneously. recording a plurality of items of image information. Hence, while the number of broadcast programs available at the same time has increased, no VTR has been capable of simultaneously recording a plurality of programs.
Meanwhile, the stereoscopic image display apparatus of the kind using the polarizing filter spectacles has presented a problem in that the feeling of stereoscopy is impaired when the viewer's face is tilted.
In the case of the stereoscopic image display apparatus of the kind using the time-division spectacles, on the other hand, the arrangement to alternately display the left and right images has caused a disagreeable feeling due to flickers.
Further, the stereoscopic image display apparatus which is shown in FIG. 2 has necessitated to display the images for the left and right eyes respectively on the two liquid crystal displays 49 and 50 in synchronism with each other. This requirement results in a complex display control circuit. Besides, the apparatus for recording the stereoscopic images also requires a complex arrangement.
Among the known stereoscopic image recording and reproducing apparatuses arranged to record on a recording medium a stereoscopic image signal for a stereoscopic image which is composed of left and right images and to reproduce the stereoscopic image signal from the recording medium, some apparatuses are arranged to record on a recording medium two-channel image signals outputted respectively from two video cameras as a one-channel stereoscopic image signal and reproduce the stereoscopic image signal from the recording medium.
The stereoscopic image recording and reproducing arrangement of the conventional apparatus mentioned above is as follows: In recording, image signals of n channels picked up by an n number of video cameras (n: an integer which is at least two) are respectively compressed to 1/n in the direction of a time base. The compressed image signals are time-divisionally multiplexed into a one-channel stereoscopic image signal before recording on a recording medium. In reproduction, the image signals time-divisionally multiplexed and time-base-compressed to 1/n are reproduced from the recording medium and separated from each other. After that, they are time-base-expanded by n times to restore them to the n-channel image signals.
In the conventional stereoscopic image recording and reproducing apparatus which is arranged as mentioned above, the time base of each of image signals of plural channels is compressed. After that, the image signals are time-divisionally multiplexed and recorded on a recording medium in the form of a one-channel stereoscopic image signal. At the time of reproduction, the reproduced stereoscopic image signal is time-base-expanded to bring it back into the original plural-channel image signals. However, in the event of time base variations such as jitters, for example, a time base variation component is also enlarged by n times in the same manner as the image signal to distort a reproduced image.
The adverse effect of the above-stated time base variations on the reproduced image conspicuously appears particularly in the luminance component of the image signal. Vertical lines in an image, such as the window sashes, the contour, etc., of a building, should be expressed in straight lines. However, in the event of occurrence of time base variations in the recording and reproducing systems, these lines are expressed as bent lines. Particularly, in the case of the conventional stereoscopic image recording and reproducing apparatus described above, the arrangement of expanding the reproduced stereoscopic image by n times in the direction of time base causes the time base variation component to be also expanded by n times. As a result, the degree to which the image is distorted is enlarged also by n times to further the image distortion.
FIG. 3 shows the states of signals and images on display obtained in the event of occurrence of time base variations when a stereoscopic image signal which is composed of an image signal for a left image and an image signal for a right image is recorded and reproduced on and from a recording medium by the conventional stereoscopic image recording and reproducing apparatus, which has been arranged in the manner described above.
In FIG. 3, a part (f) shows a one-channel stereoscopic image signal obtained by time-divisionally multiplexing the image signals of two left and right channels which are time-base-compressed to 1/2. In the part (f), reference symbol "l" denotes a signal for the left image and a symbol "r" a signal for the right image. A part (g) shows the time-base-compressed image signals of the part (f) in a state of being displayed on a display device such as a CRT. Parts (h), (i) and (j) show the time-base-compressed image signals of the part (f) in such states that are obtained when time base variations take place in a recording and reproducing system in recording and reproducing them on or from a recording medium with a recording and reproducing apparatus such as a VTR or the like. When time base variations take place in the recording and reproducing system, the adverse effect of the time base variations is relatively small on the left image which is near to a horizontal synchronizing signal, as shown in the parts (i) and (j). However, the adverse effect is quite salient on the right image and is about two times as great as the effect on the left image.
Further, while the adverse effect of time base variations on the luminance component of the image signal are as described above, the time base variations also have the n times multiplied adverse effect as variations in hue on the chrominance component of the image signal in the same manner as on the luminance component. The time base variations thus make it hardly possible to carry out a demodulation process with correct hue, and thus result in uneven colors of an image displayed.